OAB-036: Graded renal response criteria and revised renal progression criteria for light chain (AL) amyloidosis

Abstract

<h3>Background</h3> Renal light chain (AL) amyloidosis manifests as proteinuria with or without renal failure and is associated with a risk of progression to renal replacement therapy (RRT). A significant reduction in circulating amyloidogenic light chain is needed to achieve a renal response. Current renal response criteria are binary defining a renal response as >30% reduction in 24-h proteinuria without worsening estimated glomerular filtration rate (eGFR). Several studies suggest that greater reduction in proteinuria following successful therapy improves renal and overall survival. <h3>Methods</h3> AL amyloidosis patients diagnosed between 2010 to 2015, achieving at least hematological partial response to therapy and with renal involvement were included. Four renal response categories were formulated based on reduction level in pretreatment 24-h proteinuria in the absence of renal progression: renal complete response (renCR, 24-h proteinuria ≤200 mg/24-h); renal very good partial response (renVGPR, >60% reduction in 24-h proteinuria); renal partial response (renPR, 31-60% reduction in 24-proteinuria); and renal no response (renNR, 30% or less reduction). Renal response was assessed at landmark (6-, 12-, and 24 months from treatment initiation) and as best renal response. Graded renal responses were assessed as predictors for time from diagnosis to RRT and overall survival. <h3>Results</h3> Seven hundred and thirty-seven patients were included. The median age was 63. Renal stage I, II and III were assigned to 34%, 52% and 14% of patients, respectively. Reduction in 24-h proteinuria from baseline improved over time with a median reduction of 34%, 50% and 71%, at 6-month, 12-month and 24-months, respectively. At best response, renCR, renVGPR, renPR and renNR were achieved in 27%, 34%, 15% and 24% of patients, respectively. A renal response as early as 6 months after therapy initiation was able to predict time to RRT with an increase in RRT risk with lower level of renal response at that time point (5-year RRT 0%, 3%, 9% and 16% for renCR, renVGPR, renPR and renNR, respectively, P<0.001). Prediction of risk for RRT based on renal response depth improved at 12- and 24-months and at best renal response. Overall survival discrimination based on renal response depth was noted as early as 12 months from therapy initiation and improved with time. eGFR progression (≥25% decrease in eGFR) and proteinuria progression (at least 50% increase to ≥3g/day) were predictive for time to RRT. <h3>Conclusions</h3> We validated new graded renal response criteria based on reduction in 24-h proteinuria. These 4-level renal response criteria highlight the importance of achieving a deep renal response to improve renal and overall survival. These findings will allow clinicians to make decision on therapy changes or augmentation based on response depth as early as 6-month before irreversible renal failure has developed.